The present invention relates to apparatus for treating pulp of cellulosic fibre material with a treating liquid.
The distributing tubes used hitherto in apparatus of the type described are in the form of rings mounted with a space from the rotation-symmetrical wall of the vessel, which is usually cylindrical. The annular tubes communicate with the interior of the vessel via inlet connections, each having an inlet connection piece and a tube bend connected by means of a flange-bolt joint. It will be understood that such an arrangement, with annular tubes suspended outside the vessel requires extensive manufacture and assembly work, the inlet connection pieces having to be fitted into holes drilled in the cylinder wall, and welded to the cylinder wall before or after said flange-bolt joint is made. Fitting and welding the many different components is complicated. In order to obtain circular ring tubes they must be bent by means of a complicated induction technique requiring special equipment that is not usually available in workshops where the apparatus is manufactured. However, one of the main drawbacks is that the annular tubes and the inlet connections, comprising inlet connection pieces and tube bends, must be test-assembled at the workshop prior to delivery, after which the parts are dismantled and marked before being delivered to the relevant site where they are once again assembled in accordance with the markings made. Complicated and time-consuming work follows this final assembly in order to insulate the washing apparatus since each individual annular tube must be insulated and insulation must be applied to the cylinder wall inside the insulation around the annular tubes. Complicated insulation hoods with eccentric clamps must also be made and applied around the tube bends and adjacent flange-bolt joints. The insulation of the annular tubes and inlet connections is not sufficient and the annular tubes must be heated with electric current to prevent the treating liquid from freezing. Since the annular tubes have circular cross section it is difficult to connect a pipe socket with tangential or other inclined direction to the annular tubes and the pipe sockets must therefore be connected radially. This means that during operation liquid is distributed into the annular tube in both directions, thereby risking it becoming stationary at the diametrically opposite side, and fibres thus collecting there and either entirely or partially clogging the annular tube. Since the inlet connections are located above each annular tube, remaining liquid cannot be tapped from the system to the vessel when there is a stop in production.